Carrier aggregations (CAs) refer to simultaneous wireless reception of several signal channels corresponding to different frequencies in a Long Term Evolution (LTE) wireless system.
FIGS. 1-3 illustrate different carrier aggregation schemes, respectively. The intra-band continuous/non-contiguous carrier aggregation occurs when multiple component carriers locate in a same radio frequency (RF) band, as shown in FIGS. 1 and 2. The inter-band carrier aggregation occurs when multiple available component carriers locate in different RF bands, as shown in FIG. 3.
As illustrated in the intra-band contiguous carrier aggregation 100 of FIG. 1, the signal channels 102a, 102b locate in Band A and are adjacent to each other. The higher-frequency component carrier 102b may be viewed as a primary component carrier (PCC), and the lower-frequency component carrier 102a may be viewed as the secondary component carrier (SCC).
FIG. 2 illustrates an example of intra-band non-contiguous carrier aggregation 200, wherein the component carriers 202a, 202b are both in Band A but are not adjacent to each other. The higher-frequency component carrier 202b may be viewed as the PCC, and the lower-frequency component carrier 202a may be viewed as the SCC.
FIG. 3 illustrates an example of inter-band non-contiguous carrier aggregation 300, wherein the component carriers 302a and 302b are in Band A and Band B, respectively. The component carrier 302a may be the PCC and the component carrier 302b may be the SCC. In the inter-band carrier aggregation shown in FIG. 3, the two signal channels are in different reception bands.
In FIG. 2, there is only one receiving band (Band A) and two non-contiguous channels. Thus, there is a need for an innovative low-noise amplifier (LNA) design which is capable of receiving one RF input and generating two RF outputs to different mixers for down-conversion of two channels, including one PCC channel and one SCC channel. Further, since the required signal levels of the two channels, including one PCC channel and one SCC channel, may not be equal to each other, there is also a need for enabling an LNA design to support a function of using different gains for generating output signals to different mixers for down conversion.